As already known by those skilled in the art, alternative compressors comprise machines and/or devices capable of altering a working fluid pressure as well as pumping it. In this sense, and more specifically speaking, said alternative compressors are capable of altering the working fluid pressure by controllably altering the volume of a compression chamber that is usually defined by a cylindrical chamber which receives working fluid and moving piston. Hence, the compression chamber volume is alternatively altered (reduced or increased) in function of the moving piston displacement in its interior. Inlet and removal of working fluid are orderly managed by suction valves and discharge valves which have their statuses alternatively switched.
It is also known by those skilled in the art that (suction) inlet steps and (discharge) removal steps of the working fluid inside the compression chamber are crucial steps for the correct operation of an alternative compressor, which have an direct effect on the compressor performance parameters and accordingly the present state of the art comprises a wide range of valves intended to control suction and discharge of working fluid in the compressor chamber interior.
In alternative compressors used in refrigeration systems, there should particularly mentioned the use of pallet-type valves. Pallet-type valves are extremely conventional and comprise, in brief, thin metal blades with a contour which edge is the (suction or discharge) orifice sealing surface and the body connecting the sealing surface with the valve securing point.
According to more conventional embodiments, it can be noted that the present suction valves have a normally closed configuration and their automatic and not commanded “opening” occurs uniquely and exclusively when the piston is at the superior neutral point and descends towards the lower neutral point. And conventional discharge valves also have a normally closed configuration and their automatic and not commanded “opening” uniquely and exclusively takes place when the piston starts from the lower neutral point and goes towards the superior neutral point, increasing the pressure inside the cylinder, that is, when the pressure inside the cylinder is higher than the pressure in the discharge chamber.
This means that in accordance with the most conventional embodiments, operability of the present suction and discharge valves is based on the working frequency of a compressor, wherein pallets are designed to give rapid responses and reduced bending strain.
Pallet-type suction and discharge valves, in which the operational status is selectively switched by actuation of at least a magnetic field-generating element, are also known. An exemplary embodiment of this concept is disclosed in the BR Patent Application P11105379-8.
According to BR P11105379-8, the present state of the art further provides a semi-commanded valve system applied to an alternative compressor comprising pallet-type valves which once pre-stressed in a first operational status can be switched to a second operational status through actuation of electric coils duly aligned to the respective valves thereof.
Said system also permits to modulate the compressor capacity with no need to vary the operational speed of its electric motor such that the amount of mass that passes through the suction orifices and discharge orifices can be controlled.
Although the valve system described in this document BR P11105379-8 achieves the desired objectives it is further observed that same does not comprise means capable of checking the status of the suction and discharge valves.
This means that the valve system disclosed in BR P11105379-8, in addition to the remaining valves systems known from the present state of the art, are not capable of checking whether or not the real operational status of a valve corresponds to the system-commanded operation status, that is, checking whether or not a suction valve is really opened or closed in the cycles during suction cycles.
The closest embodiment for effecting such checking is found in patent document CA2622067, which refers to a system (for screw compressor) wherein an angularly movable metal component has it movement measured by a magnetic sensor that generates an electric signal to a processor, wherein the distance variation between the metal component is capable of inducing a magnetic field measurable in a sensor.
Therefore, it can be noted that said system taught by CA2622067 is capable estimating the “location” of a movable component of a screw compressor. However, it does not teach how to measure the operational status of linearly alternative performance valves.
Based on this context, the present invention was developed.